Patent GB-755929-A (GB)
Title: Improvements in cold-cathode gas-discharge tubes
Inventor: TOSSWILL CHRISTOPHER HALY
IPC: H01J17/48
Filed: 1952-08-27
Abstract: 755,929. Multi-gap cold-cathode tubes. MULLARD RADIO VALVE CO., Ltd. July 30, 1953 [Aug. 27. 1952], No. 21549/52. Class 39 (1). [Also in Group XIX] A cold cathode gas-discharge counting tube, shown in developed form in Figs. 1 and 2, comprises a disc anode 7 surrounded by a ring of ten cathodes 2 each having a narrow plane portion a and a wide curved portion b to provide a directional effect. Adjacent the cathodes 2 is a series of probe electrodes 3, each extending from the centre of the curved portion b of a cathode to the plane portion a of the adjacent cathode and having its body arranged at such a distance from the cathodes as to be just on the anode side of the edge of the cathode fall zone. Between the probe electrode 3 and the anode 7 is a cylindrical screen 4 provided with rectangular apertures 5, one opposite each of the cathodes 2. Ten input electrodes 6 are provided between the screen 4 and anode 7, each being radially in line with one end of a probe electrode 3 and the portion a of a cathode 2. The electrode structure is mounted between two mica discs 34 and enclosed in a glass envelope (not shown) which is filled with a mixture of 50 per cent argon and 50 per cent neon at a pressure of 15 mm. of mercury. In an alternative construction the cathodes are of plane rectangular form and the directional effect is obtained by making the apertures in the screen 4 of keyhole shape as described in Specification 755,928. The circuit shown in Fig. 6 comprises two tubes 1 and 10 connected for cascade operation. The tube 1 has a common anode 7 connected through a resistance 17 to the terminal 32 of a source of positive potential and ten cathodes of which the zero cathode 2<SP>0</SP> and four cathodes 2<SP>1</SP>-2<SP>1111</SP> representing the first four digits are shown. Alternate cathodes are connected together to form two groups each of which is connected through a resistance-capacity network to the earth line 31 and the zero cathode 2<SP>0</SP> is connected through an individual resistance-capacity network to earth. The input electrodes 6 are connected together to an input terminal 36 and through a resistance 18 to the terminal 33 of a source of positive potential considerably lower than that connected to terminal 32. The screen 4 is connected through a resistance 19 to the terminal 33. The probe electrodes (not shown) are floating except for the probe 3 between the zero and first cathodes which is connected through a resistance 8 to earth and through a condenser 9 to the input electrodes 60 of the tube 10 which has ten cathodes 20, probes 30, screen 40 and an anode 70 corresponding to the electrodes of tube 1. A discharge between the anode 7 and say cathode 2<SP>1</SP> will concentrate at the curved portion b of the cathode or at the part of the cathode opposite the circular portion of the keyhole aperture in the screen 4 depending on which form of cathode and screen construction is used. The potential of the probe having one end adjacent this portion of the cathode will thus be raised and a small priming discharge occurs between the other end of the probe and the portion a of cathode 2<SP>11</SP>. This discharge is unable to initiate a discharge between the anode 7 and cathode 2<SP>11</SP> owing to the presence of the screen 4 which is considerably negative with reference to the anode, but if a positive-going pulse is applied to the input electrodes 6, the priming discharge extends through the aperture 5 in the screen 6 and initiates a discharge between the anode 7 and the portion a of cathode 2<SP>11</SP>, which discharge moves automatically to the portion b of the cathode, and the discharge at cathode 21 is extinguished. The discharge is thus stepped one cathode along the array for each positivegoing pulse applied to the terminal 36 and the number of pulses received can be determined by a visual inspection of the position of the glow discharge or by electrical connections to the various cathodes or probe electrodes. On receipt of the tenth pulse the discharge returns to the zero cathode 2<SP>0</SP> and the potential of the probe 3 is raised so that a positive-going pulse appears across the condenser 9 and is applied to the input electrodes 60 of tube 10. In the same way an output pulse is passed to the output terminal 35 on receipt of the hundredth pulse.